[Varyon]

I don't think this was ever handled, but the Illumination Table from P:ES implies that a default character's eyes are (provided you get there gradually or at least adapt quickly) at +0 between 100 and 200,000 lux of illumination. That's a range of 2,000x, or 5 steps on the table.

How does this "free" range band work for characters with the Night Vision Feature (Night Vision that costs nothing, because you are penalized by bright light)? Does the character lose it by having that Feature? It seems unfair to do so, yet maintaining it could be unbalanced. For example, light levels above 2,000 lux are going to be moderately uncommon (that's around the maximum for midday on an overcast day), so Night Vision 3 [0] basically eliminates up to -3 in Darkness penalties with the only real drawback being a small penalty if you're outside on a bright day.